Cooling system for air cooled internal combustion engine



June 18, 1957 L. J. LECHTENBERG I 2,796,053

COOLING SYSTEM FOR AIR COOL-ED INTERNAL COMBUSTION ENGINE Onginal Filed May 11, 1953 4 Shams-Sheet 1 June 18, 1957 1.. J. LECHTENBERG 2,796,053

v COOLING SYSTEM FOR AIR COOLED INTERNAL COMBUSTION ENGINE Original Filed May 11, 1953 4 Shasta-Sheet 2 M704. .ZM JlM/Zimbm'q June 18, 1957 L. J. LECHTENBERG 2,796,053 COOLING SYSTEM FOR AIR COOLED INTERNAL COMBUSTION ENGINE Original Filed May 11, 1953 4 Sheets-Sheet 3 June 18, 1957 L. J. LECHTENBERG 2,796,053

COOLING SYSTEM FOR AIR COOLED INTERNAL COMBUSTION ENGINE Original Filed May 11, 1953 4 Sha na-Sheet. 4

- .Zm jJm/zimbpr;

United States Patent O COOLING SYSTEM FOR AIR COOLED INTERNAL COMBUSTION ENGINE Leo J. Lechtenberg, Milwaukee, Wis., as'signor to Briggs & Stratton Corporation, Milwaukee, Wis., a corporation of Delaware Original application May 11, 1953, Serial No. 354,056, now Patent No. 2,693,789, dated November 9, 1954. Divided and this application November 8, 1954, Serial No. 467,597

8 Claims. (Cl. 1234l.65)

This invention relates to internal combustion engines and refers more particularly to a cooling arrangement for a single cylinder air-cooled, four stroke cycle engine of the type used on power lawn motors and many other well-known appliances.

As in the copending application, Serial No. 354,056, now Patent No. 2,693,789, of which this application is a division, this invention has as its main purpose the production of a lighter engine at less cost. To this end the present invention has as one of its objects to provide an improved cooling arrangement for the engine.

More specifically, one of the features of the present invention resides in the provision of an air directing wall or bafiie formed as an integral part of the cylinder castingand disposed tangentially to all of the cooling fins on the cylinder so that a portion of the die or mold in which this wall is cast may be used as a large capacity gate through which the molten metal may be quickly passed This assures into the cylinder-forming part of the die. the desired metal density in the cylinder walls where casting defects would be most serious.

Another object of this invention is to use the metal name plate with which engines have always been equipped as part of the air directing means. Accordingly, the nameplate is fastened to the side of the cylinder with one edge of the nameplate contiguous to the bafile which is cast integral with the cylinder and extends across an ad jacent side of the cylinder.

With these and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is an end view of the engine of this invention viewing the same from the flywheel end of its crankshaft, parts of said view being broken away to show structural details; I

Figure 2 is a side viewof the engine shown in Figure 1 with parts thereof broken away and in section and with the carburetor removed for clarity;

Figure 3 is a view of the power take-off end of the engine with the engine nameplate broken away to show a portion of the cylinder and the cooling fins cast integrally therewith;

Figure 4 is a perspective view of the upper portion of the crankcase cylinder casting viewed from substantially the same side thereof shown in Figure 1 and with attention directed particularly to the cylinder portion of the casting; and

Figure 5 is a perspective view of the upper portion of Patented June 18, 1957 ICC 2 the crankcase cylinder casting viewed from the side opposite that shown in Figure 4.

Referring to the accompanying drawings in which like numerals indicate like parts throughout the several views, the numeral 5 designates generally the crankcase-cylinder casting of the engine, consisting of a crankcase portion 6 and a cylinder 7. This main casting together with a cylinder head 8 and a crankcase cover 9 comprise the entire body of the engine.

The crankcase-cylinder casting 5, the cylinder head 8 and the crankcase cover 9 are cast of aluminum alloy, and to achieve the primary purpose of the invention, these parts, and especially the crankcase-cylinder unit 5 must be die castable. Being die castable, it follows of course that these parts can be produced as sand-castings. However, since the greatest economy is effected by die casting, this form of casting is preferred over the sand casting method.

The crankshaft 10 and its cam shaft are journalled in hearings in the cover casting 9 and the end wall 11 of the crankcase-cylinder casting opposite the cover; and the flywheel 12 is mounted upon the end of the crankshaft which protrudes from the casting wall 11. The opposite, power take-off end of the crankshaft protrudes from the cover casting. The crankshaft is of conventional construction and is drivingly connected with a piston, not shown, by the customary connecting rod, also not shown.

The cylinder head 8 is of conventional construction with cooling fins 13 cast integrally therewith, and has the usual spark plug 14 mounted therein. The cylinder cooling fins 16 are cast integrally with and encircle the cylinder 7, and other cooling fins 17 are cast integrally with a boss-like portion 18 of the crankcase-cylinder casting. The intake port 19 and the exhaust port 20 are located in this boss-like portion 18 and the front face of the portion 18 is flat and has the attaching flange 21 of the carburetor and air cleaner assembly indicated generally by the numeral 22 bolted thereon. The fins 17 are in line with the adjacent cylinder cooling fins 16 and below the boss-like portion 18 the cylinder fins 16 are extended to also embrace a portion 23 of the crankcasecylinder casting in which the stem of the exhaust valve slides. Except where the fins 16 merge with and in effect become the fins 17, and where they embrace the portion 23, the peripheral-edges of the intermediate fins, that is, those inwardly of the uppermost and lowermost'fins, are substantially arcuate andequidistant from the cylinder wall.

The flywheel 12 is equipped with the customary fan blades 25 which induce a flow of cooling air into the inlet of a shroud 26 and from the outlet thereof against the adjacent side of the cylinder. The inlet of the shroud is protected by the customary rotary screen 27 which is preferably mounted upon a rope starter pulley 28 suitably secured to the adjacent end of the crankshaft.

A portion of the shroud 26 is substantially cylindrical and snugly fits a correspondingly shaped ridge 30 on the casting wall 11 with the adjacent edge of the shroud lying flat against the face of the wall 11. The shroud is held in this position by screws 31 threaded into bosses 32 on the casting. The upper discharge portion of theshroud has substantially flat opposite walls 33 connected by a top wall 34. The edge of this top wall is contiguous to a separate sheet metal cylinder head cover 35 disposed across the top of the cylinder head fins to direct part of the air issuing from the shroud across the top of the cylinder head between the cooling fins thereon.

The side of the cylinder diametrically opposite the side thereof at which the carburetor and the intake and exhaust ports are located is covered by a thin flat wall 36 which extends in a longitudinal direction at least from the uppermost fin 16 to the lowermost fin 16 and has a width at least equal to the diameter of the fins. This wall serves several purposes. It is cast integrally with the crankcase-cylinder casting and is tangentially contiguous to and joins with all of the cylinder cooling fins 16 along a median plane which contains the. cylinder axis and is perpendicular to the wall 36. The wall extends laterally to opposite sides of this median plane and terminates in straight parallel side edges which lie in spaced planes substantially tangent to the edges of the cylinder cooling fins and parallel to the said median plane of the engine. As will appear hereinafter, it is significant that the wall 36 is parallel to the crank-shaft axis.

At the side of the cylinder diametrically across from the shroud 26 the edges of the uppermost and lowermost fins, that is, the axially endmost heat dissipating fins, are straight and perpendicular to the wall 36. These straight edges join the wall 36 at the adjacent side edges thereof. As a result, the axially endmost fins may be said to have triangular corner portions 37 to enable these fins to better coact with the wall 36 in directing and confining the air which issues from the discharge end of the shroud and flows transversely across the cylinder between the fins. Also for this purpose the wall 36 is contiguous to the edge of the adjacent side wall 33 of the shroud so as to form in effect an extension of said shroud wall.

The air directing effect of the flat wall 36 in conjunction with the corner portions 37 of the upper and lower cooling fins is continued by the engines customary stamped metal nameplate 38. A single screw 39 threaded into a boss 40 formed as an enlargement of one of the cooling fins 16, secures the nameplate across the side of the cylinder opposite the shroud with one edge of the nameplate contiguous to the adjacent edge of the flat wall 36 and its upper and lower edges contiguous to the straight adjacent edges of the top and bottom cooling fins. The nameplate thus coacts with the wall 36 to direct the cooling air and cause it to effectually contact the cooling fins. It will be appreciated that this arrangement eliminates the curved air shield which heretofore was separately attached to the engine.

By reason of the fact that the wall 36 is cast integrally with the crankcase-cylinder casting and joins all of the cylinder cooling fins in the manner described, still another very important advantage is obtained, for as will be apparent to those skilled in the die casting art, the portion of the die cavity or mold in which the wall 36 is cast provides an excellent gate through which the molten metal may rapidly flow to quickly fill up the portions of the die in which the cylinder per se is cast. This assures the desired metal density in that portion of the casting where imperfections would be most serious.

In die casting the cylinder-crankcase casting, the halves of the mold must separate with a translatory motion parallel to the crankshaft axis; and to enable such rectilinear separation of the mold halves, the wall 36 must be so disposed and shaped that any straight line contained within the wall and lying in a plane normal to the cylinder axis and connecting points on the opposite side edges of the wall must be parallel to the crankshaft axis. This would permit curvature of the wall in a longitudinal direction or other non-parallel relationship with respect to the cylinder axis, but since the wall is preferably fiat, in its preferred form the wall lies in its entirety in a single plane parallel to the crankshaft axis.

Also since the wall 36 is thin and is integrally joined to each of the cylinder cooling fins it provides additional extended surface for the cylinder to thus assure more rapid dissipation of the heat generated in the engine.

It should be observed that since the wall 36 bears against the adjacent edge of the nameplate it enables the single fastening screw 39 to hold the nameplate in place.

Another advantage of the wall 36 is the protection against breakage which it affords the cooling fins during handling of the engine before the fuel tank is mounted.

The fuel tank 41 is conveniently supported by a bracket arm 42 bolted to the top of the cylinder head and a bracket 43 bolted to the outer face of the wall 36 by a screw 44 which is tapped into a boss 45 at the back of the wall 36. Hence, the wall 36 is interposed between the fuel tank and the enginecylinder and shields the fuel tank against the heat radiated from the cylinder, the heat thus intercepted by the wall 36 being carried away by the cooling air flowing across its inner surface.

From the foregoing description taken in connection with the accompanying drawings, it will be apparent that this invention provides a cooling arrangement for internal combustion engines which is not only efficient for its intended purpose but is highlyv advantageous from the standpoint. of simplicity and manufacturing procedure.

What I claim as my invention is:

1. An air cooled internal combustion engine having a cylinder with integral heat dissipating fins encircling the same and having a fuel tank mounted alongside the cylinder but spaced therefrom, said engine also having a blower fan and a shroud for directing air discharging from the fan against a side of the cylinder adjacent to the side thereof which faces the fuel tank, characterized by a thin substantially flat wall between the fuel tank and the cylinder and substantially in line with one side wall of the shroud to direct air issuing from the shroud against the cylinder so that the air issuing from the shroud flows across the inner surface of said wall whereby said wall serves to shield the fuel tank from heat radiated from the cylinder, said wall being integrally joined to the fins to thereby also increase the extended cooling surface provided by the fins.

2. An air-cooled internal combustion engine having a cylinder with integral heat dissipating fins encircling the same, a blower fan and a shroud at one side of the cylinder for directing air discharging from the fan against said one side of the cylinder and between the fins: characterized by a thin wall covering but spaced from one side of the cylinder and substantially in line with one side wall of the shroud to direct air issuing from the shroud against the cylinder; said wall lying in its entirety substantially in a single plane parallel to the crankshaft axis of the engine so that said wall does not interfere with die casting of the cylinder in a mold the halves of which separate with a translatory motion parallel to the crankshaft axis; said thin fiat wall being integrally joined to the fins and thereby augmenting the extended surface provided by the fins.

3. The internal combustion engine defined in claim 2 further characterized by the provision of a sheet metal shroud-forming plate covering the finned side of the cylinder diametrically across from the side thereof at which the shroud is located; and means securing the shroud forming plate in place with one side edge of the plate contiguous to one side edge of said thin flat wall and with said plate disposed substantially at right angles to said thin flat wall so that cooling air which has flowed between the cylinder and said thin flat wall is constrained to fiow between the cylinder and said shroud forming plate.

4. The air-cooled internal combustion engine of claim 2 further characterized by the fact that the edges of the axially endmost heat dissipating fins on that side of the cylinder diametrically across from the side thereof at which the shroud is located are straight and perpendicular to said thin fiat wall and join said thin fiat wall at the adjacent side edge thereof; a sheet metal nameplate for the engine of a size to span the distance between said axially endmost heat dissipating fins and to extend from the adjacent side edge of said thin flat wall across the cylinder; and means removably fastening said nameplate to the cylinder with one side edge thereof contiguous to said thin flat wall and its two adjacent edges contiguous to said straight edges of the axially endmost fins so that the nameplate coacts with said axially endmost fins and the thin flat wall to direct the air flowing between the fins against'the cylinder.

5. In an air-cooled single cylinder internal combustion engine, a die-castable cylinder casting having a cylinder forming portion and heat dissipating fins integral with and encircling the cylinder, said casting being characterized by a thin wall lying in its entirety substantially in a single plane alongside and spaced from the cylinder, said wall being wider than the diameter of the cylinder and being integrally joined to the heat dissipating fins so as to augment the extended surface provided by the fins and also guide and direct the flow of cooling air transversely across the cylinder and between the fins; the plane of said wall being parallel to the crankshaft axis of the engine so that the wall does not interfere with the formation of the casting by die casting the same in a mold the halves of which separate with a translatory motion parallel to the crankshaft axis.

6. In an air-cooled single cylinder internal combustion engine, the die-castable cylinder casting of claim 5 further characterized by the fact that said thin fiat wall is integrally joined to all of the fins at portions thereof bisected by a plane containing the cylinder axis and perpendicular to said thin fiat wall so that molten metal entering the mold in which the casting is made, at the portion of the mold in which the thin flat wall is formed, flows quickly and directly to that part of the mold in which the cylinder walls are formed to thus afford good assurance against casting imperfections in the cylinder walls.

7. In an air-cooled single cylinder four stroke cycle internal combustion engine: a die-castable one piece cylinder and crankcase casting, one portion of which provides the cylinder and its integral heat dissipating fins encircling the cylinder and which portion of the casting also has the intake and exhaust ports therein at one side of the cylinder, and another portion of which provides all walls of the crankcase except one of the two walls thereof in which the crankshaft bearings are located; said casting being characterized by a thin wall lying in its entirety substantially in a single plane alongside but spaced from the cylinder side thereof diametrically across from the side of the cylinder at which the intake and exhaust ports are located, said wall covering the side of the cylinder to which it is adjacent and being integrally joined to the heat dissipating fins so as to augment the extended surface provided by the fins and also guide and direct the flow of cooling air transversely across the cylinder and between the fins; the plane of said thin flat Wall being parallel to the crankshaft axis so that the wall does not interfere with the fiommation of the casting by die casting the same in a mold the halves of which separate with a translatory motion parallel to the crankshaft axis.

8. In an air-cooled single cylinder internal combustion engine, a die-castable cylinder casting having a cylinder forming portion and heat dissipating fins integral with and encircling the cylinder, said casting being characterized by a thin wall alongside and spaced from the cylinder, said wall being wider than the diameter of the cylinder and having opposite side edges, said wall being so disposed and shaped that any straight line contained Within the wall and lying in a plane normal to the cylinder axis and connecting points on said opposite side edges of the Wall is parallel to the crankshaft axis of the engine, so that the well does not interfere with the formation of the casting by die casting the same in a mold the halves of which separate with a translatory motion parallel to the crankshaft axis, and said wall being integrally joined to the heat dissipating fins so as to augment the extended surface provided by the fins and also guide and direct the flow of cooling air transversely across the cylinder and between the fins.

References Cited in the tile of this patent UNITED STATES PATENTS 2,031,891 Irgens Feb. 25, 1936 FOREIGN PATENTS 574,161 Great Britain Dec. 21, 1945 

